I believe there's a kit available for mounting the transducer to the TM if you don't already have it.
I would be interested to know of this kit....
SUAF, Does the mounting bracket you have come with the Xi5 or is that aftermarket?
The Mounting bracket for the Xi5 is aftermarket. It is the LiftSaver Trolling Motor Mounting Bracket.
http://www.shut-up-and-fish.com/liftsaver-trolling-motor-mounting-bracket-c-156.html The bracket for the HDI transducer on the TM is part#: 000-10978-001
LOWRANCE HDI TROLLING MOTOR ADAPTER CUP F/SKIMMER XDCR
000-10978-001
$19.95